His first singles match on grass as he prepares to defend the Wimbledon title wasn't all smooth sailing but Federer was never really threatened.

"I'm always pleased when I win, no matter how I win," Federer said.

Gael Monfils reached the quarterfinals as well, then announced he will miss Wimbledon.

After defeating Czech qualifier Jan Hernych 6-2, 6-3, Monfils said he withdrew his request for a Wimbledon wild card because he had to deal with a personal problem that could not be delayed. He didn't elaborate.

Mikhail Youzhny also advanced to the last eight by upsetting fourth-seeded Kei Nishikori 6-1, 6-7 (4), 6-3. German wild card Mischa Zverev went through by beating Mirza Basic 7-6 (5), 6-3 after coming from behind in both sets.

Four of Federer's seven Wimbledon titles have come after Federer had also won the tuneup event in Halle. His link to the Halle event is so deep that he has had a street named after him.

Now ranked No. 3 in the world, Federer has not won a title this year and is coming off a quarterfinal loss at the French Open.

Serving for the first set, Federer produced four straight errors to waste two set points and drop his serve with some very sloppy play. He bounced back in the next, however, to win the set.

Federer hit two wild backhands to help Stebe hold his serve in the seventh game of the second. Federer also committed a double-fault on his first match point, but hit a volley winner to end it.

"I got an early double-break lead in the first, I got up a break in the second, it was pretty straightforward," said Federer, who next faces Zverev.

Monfils was once ranked No. 7 in the world but the Frenchman missed several months last year because of a knee injury. He was ranked No. 119 in May before moving up to No. 67.

Monfils, who has never passed the third round at Wimbledon, said it was a pity he would have to miss it for the second straight year and fourth time in six years, especially because he felt he was beginning to play better on grass.

For a player who says he has trouble moving on grass, Monfils was at his acrobatic best against Hernych.

At one point, he even jumped over the net. Trying to save a break point, the Czech qualifier dived to his right to reach a ball at the net and managed to send it over. Monfils raced forward, failed to reach it in time and his momentum carried him over the net. The two touched hands and Monfils got back to his side to eventually break serve for a decisive 4-2 lead in the second set.

The Frenchman's enthusiasm did not always result in points - he once jumped high for a smash, only to rip it into the net. But another time, he chased down a lob and hit a perfect backhand winner on the turn.

"I was happy, I was having fun," Monfils said. "Grass is not natural for me, but I am getting better. I have to focus on not falling, not injuring myself. I cannot take off as fast as I want to and I have problems braking. But I was comfortable today, I was leading all the time."

Youzhny was not quite as spectacular as Monfils but his steady game carried him past Nishikori in the first set.

"He started well, he was hitting a lot of first serves and I was missing everything," the Japanese said.

Nishikori said it was not easy to adjust to grass and that he would remain in Halle for a while to practice more and play doubles.

Youzhny was twice a semifinalist in Halle, including last year, and lost to Roger Federer both times.

Basic, a Bosnian who upset seventh-seeded Jerzy Janowitz in his first match in the main draw of an ATP Tour event on Tuesday, squandered a 4-1 lead in the first set and a 2-1 break lead in the second. He saved three match points on his serve but Zverev closed it out with a service winner.